Formation and Destruction of Pyrimidine Dimers in Polynucleotides by Ultra-violet Irradiation in the Presence of Proflavine

Abstract

THE ultra-violet irradiation of polynucleotides in solution results in the reversible formation of dimers of cyclobutane type between adjacent pyrimidine residues¹. In DNA, such dimers produce important effects in many biological systems². Beukers has also found that the presence of proflavine during irradiation at 2537 Å inhibits the formation of thymine dimers in DNA and that dimers produced in the absence of proflavine are destroyed by further irradiation in its presence³. Although Beukers was unable to show that the destruction of the dimers in DNA consists of a simple reversion to monomers, he suggested that this might be demonstrated by means of experiments with organized polymer dI.dC consisting of strands of polydeoxyinosinic acid and polydeoxycytidylic acid. Such a polymer has already been used to show that the enzymatic destruction of uracil dimers by photoreactivating enzyme in the presence of visible light consists of monomerization¹.